The present invention relates to thermally or temperature responsive valves of the type operative to valve a vacuum control signal port for connections between a plurality of vacuum source signals in response to experiencing preselected temperatures. Valves of this type are employed in automotive engine control applications where it is desired to provide a connection between a vacuum control signal port or line and a vacuum source having a known magnitude or characteristics when desired engine temperature is sensed for providing vacuum actuation of an engine accessory or control device.
In particular thermally responsive or temperature sensing valves are employed in automotive applications for switching or valving engine manifold vacuum to a vacuum control signal line for actuating a vacuum operated distributor timing advance mechanism upon engine coolant temperature reaching a preselected temperature. Typically, in such engine applications the manifold vacuum is closed from the control signal line and a ported venturi suction signal is employed for controlling the advance mechanism for cold engine operation prior to the engine coolant reaching a preselected temperature.
Temperature responsive vacuum valves for such automotive engine applications have heretofore employed a three-port valve arrangement having a valving member with a plurality of annular seals disposed thereon for axial movement between positions alternately seating and unseating the annular seals against spaced valve seats provided in the body of the valve. An example of such known devices is that described in U.S. Pat. No. 4,085,775, issued in the name of E. T. Steele, Jr.
In typical automotive engine applications, three-port thermally responsive vacuum valve have the temperature sensing unit threadably received in the engine block for exposure to coolant, with the housing portion having the vacuum connectors thereon disposed externally of the engine block for vacuum hose attachment thereto. In providing devices of this kind for installation on an engine block, it is required that the housing and vacuum line connectors extend outwardly from the engine block a minimal distance in order to provide adequate clearance for engine installation in the vehicle and for subsequent attachment of engine accessories without interferring with or mechanically damaging the valve. Thus it has been desired to provide a three-port thermally responsive vacuum valve for automotive engine applications which, upon installation in an engine block, extends outwardly therefrom a minimum distance and yet provides ease of access to the vacuum port connectors. Furthermore, it has been desired to provide such a three-port vacuum valve with a minimum housing length and having a simplified construction and ease of assembly which enables the valve to be manufactured at a minimum cost.